The journalists were among seven people detained by the military on Monday as they left a drugs-burning ceremony.
The journalists were among seven people detained by the military on Monday as they left a drugs-burning ceremony organised by the Ta'ang National Liberation Army (TNLA), one of several rebel groups fighting the state.
The journalists, who have been held incommunicado since then, included reporters from The Irrawaddy and DVB, which for years challenged the former junta's iron grip on free expression with their covert reporting.
They are expected to be charged under the Unlawful Associations Act, under which a meeting with "unlawful associations" is punishable by up to three years in prison.
The legislation was widely used by the former military junta who stepped down in 2011, paving the way for the pro-democracy party of former activist Aung San Suu Kyi to take power last year.
"It's true that they broke the law by going to meet ethnic groups," Suu Kyi's senior aide Win Htein, himself a former political prisoner, told the Central News Bureau broadcaster.
He said it was wrong for the army to initiate proceedings but insisted that "the government should take action" against the journalists.
The military said Monday the group was stopped near Phayargyi village in the eastern state of Shan, not far from where TNLA fighters have been clashing with the army.
Several soldiers and four insurgents have been killed since fresh fighting erupted last week after troops discovered a training camp for the ethnic armed group, state media reported Wednesday.
The clashes come just weeks after Suu Kyi met several ethnic insurgent groups, including the TNLA, at talks aimed at ending decades of fighting in Myanmar's borderlands.
"Getting peace is more important than amending this (Unlawful Associations) Act," said Win Htein.
The detention of the journalists has drawn condemnation from activists and diplomats concerned at growing curbs on press freedom.
The Committee to Protect Journalists' Asia Program coordinator Steven Butler called the arrests an "affront to democracy in Myanmar".
It comes amid a groundswell of activism among local journalists aimed at quashing a controversial broadly-worded online defamation law which has been used to curb criticism of the government and army.
Prosecutions under the legislation have surged since the National League for Democracy came to power last year, with social media satirists, activists and journalists increasingly targeted.